client: fix go vet error at tip
client: fix go vet error at tip

OyTao/etcd_learning,rchicoli/etcd,sebrandon1/etcd,linuxcer/etcd,mickep76/etcd,nekto0n/etcd,mqliang/etcd,rchicoli/etcd,sebrandon1/etcd,endocode/etcd,handsomesun/etcd,etcd-io/etcd,hongchaodeng/etcd,westhood/etcd,achanda/etcd,rnaveiras/etcd,dannysauer/etcd,tguangch/etcd,swingbach/etcd,visheshnp/etcd,jonboulle/etcd,nekto0n/etcd,jonboulle/etcd,wantonsolutions/dinv-etcd,visheshnp/etcd,StorReduce/etcd,swingbach/etcd,ajityagaty/etcd,jlamillan/etcd,glycerine/etcd,qqsun8819/etcd,fanminshi/etcd,OyTao/etcd_learning,cockroachdb/etcd,lumjjb/etcd,xiang90/etcd,endocode/etcd,ravigadde/etcd,bdarnell/etcd,insequent/etcd,sofuture/etcd,StorReduce/etcd,wantonsolutions/dinv-etcd,sofuture/etcd,mickep76/etcd,mkumatag/etcd,achanda/etcd,heyitsanthony/etcd,bluebreezecf/etcd,sinsharat/etcd,tguangch/etcd,a-robinson/etcd,mqliang/etcd,siddontang/etcd,ravigadde/etcd,siddontang/etcd,ktateish/etcd,joshix/etcd,dnaeon/etcd,armstrongli/etcd,xiang90/etcd,joshix/etcd,coreos/etcd,plasticbox/etcd,purpleidea/etcd,akauppi/etcd,cockroachdb/etcd,YuleiXiao/etcd,tamird/etcd,jlamillan/etcd,linuxcer/etcd,gyuho/etcd,yudai/etcd,mqliang/etcd,coreos/etcd,luxas/etcd,heyitsanthony/etcd,whuwxl/etcd,zaphod-concur/etcd,wantonsolutions/dinv-etcd,fanminshi/etcd,rnaveiras/etcd,tamird/etcd,dnaeon/etcd,zaphod-concur/etcd,chipironcin/etcd,lorneli/etcd,bluebreezecf/etcd,glevand/coreos--etcd,lumjjb/etcd,qqsun8819/etcd,a-robinson/etcd,CrazyJvm/etcd,yudai/etcd,ajityagaty/etcd,ktateish/etcd,vimalk78/etcd,akauppi/etcd,li-ang/etcd,vimalk78/etcd,chipironcin/etcd,whuwxl/etcd,plasticbox/etcd,sinsharat/etcd,bdarnell/etcd,luxas/etcd,CrazyJvm/etcd,rnaveiras/etcd,lorneli/etcd,etcd-io/etcd,glevand/coreos--etcd,gyuho/etcd,insequent/etcd,hongchaodeng/etcd,armstrongli/etcd,mkumatag/etcd,westhood/etcd,mkumatag/etcd,etcd-io/etcd,YuleiXiao/etcd,li-ang/etcd,handsomesun/etcd,ajityagaty/etcd,purpleidea/etcd,dannysauer/etcd,glycerine/etcd